New Pd/hierarchical macro-mesoporous ZrO2, TiO2 and ZrO2-TiO2 catalysts for VOCs total oxidation

Macro-mesoporous ZrO2, TiO2 and ZrO2-TiO2 have been synthesized and used as catalytic supports for volatile organic compounds (VOCs) oxidation. These supports present high surface areas. Stability of the porous structure is observed after calcination at 400 degrees C for ZrO2-TiO2 and TiO2 but partial breakdown of the structure occurs for ZrO2 by the crystallization into tetragonal phase. All these Pd impregnated catalysts are found to be powerful catalysts for total oxidation of toluene and chlorobenzene. Pd/TiO2 presents the highest catalytic potential. The lowest toluene adsorption enthalpy, the low coke content observed after the catalytic test, PdO particles easily reducible should explain the interesting catalytic behaviour of Pd/TiO2. However, production of polychlorinated compounds PhClx (with x=2-6) occurs at low temperature during the chlorobenzene oxidation and this amount is lower over Pd/TiO2-ZrO2 compared to Pd/TiO2. But chlorobenzene is readily converted into HCl, CO2 and H2O at a temperature of 530 degrees C. (C) 2006 Elsevier B.V. All rights reserved.